DIFFERENTIAL INDUCTION AND ACCUMULATION OF BETA-1,3-GLUCANASE AND CHITINASE ISOFORMS IN SOYBEAN HYPOCOTYLS AND LEAVES AFTER COMPATIBLE AND INCOMPATIBLE INFECTION WITH PHYTOPHTHORA-MEGASPERMA F-SP GLYCINEA

Phytophthora megasperma f.sp. glycinea infection greatly induced the s ynthesis and accumulation of beta-1,3-glucanases and chitinases in hyp ocotyls and leaves of soybean seedlings. Native polyacrylamide gel ele ctrophoresis and isoelectric focusing were used to identify and quanti fy the isoforms of the two hydrolases in soybean tissues. Some beta-1, 3-glucanase isoforms were constitutively expressed in soybeans, but ot her isoforms only accumulated in soybean or only in a particular organ of soybean after inoculation with P. m. f.sp. glycinea infection or a fter treatment with mercuric chloride. The pI 8 . 4 isoform, Gb 2 of b eta-1,3-glucanase constitutively present in soybean hypocotyls and lea ves completely disappeared after mercuric chloride treatment. P. m. f. sp. glycinea infection and mercuric chloride treatment leads to the ac cumulation of distinctly different isoforms of chitinase in soybean ti ssues. The acidic chitinase isoform Ca 4 was induced and accumulated i n hypocotyls, bur not in leaves, after pathogen infection and mercuric chloride treatment. In general, beta-1,3-glucanase and chitinase isof orms accumulated in the diseased soybean tissues during symptom develo pment in both compatible and incompatible interactions. The results al so suggest that pathogen infection and chemical stress may function in a different organ-specific manner to induce isoforms of beta-1,3-gluc anase and chitinase in soybeans. (C) 1996 Academic Press Limited.